The present invention relates to guidance systems for missiles, and more particularly to a terminal homing guidance system.
Both command and homing guidance systems have been used for guidance of small missiles such as anti-tank missiles, for example. Command guidance schemes provide some type of command to the missile from a ground launcher position to direct the missile to a line-of-sight flight to the target. The commands are transmitted to the missile by a radio-frequency link, a laser link or by wire, the necessary calculations being performed at the launcher by a ground-based computer with associated sensors, or by the operator. Such a system has many disadvantages since the ground equipment is heavy and complex, wire-guidance systems are limited in range, and operator-command systems have limited performance capability as well as requiring the operator to be exposed during the flight of the missile.
Homing guidance systems utilize an on-board sensor carried on the missile to detect the target, and the command calculations are performed on board the missile. Proportional navigation or some type of pursuit guidance is usually used in these systems. Proportional navigation requires the use of inertial stabilization by means of gyros to maintain the inertial line-of-sight orientation for reference purposes to direct the missile. This type of system, therefore, involves the use of relatively sophisticated hardware and computers, and results in systems which are large and heavy as well as expensive. Where high accuracy requirements are involved and cost is not a primary factor, however, high performance systems of this type have frequently been used. Pursuit guidance systems which control only attitude and/or velocity direction are inexpensive since they avoid the requirement for inertial stabilization. These systems, however, have relatively low performance capability and can be used only for stationary targets or targets which maneuver at quite low speed.